Here is a really quick and easy nintendo switch controller grip. Its really simple and quick to print. Might not look amazing but it feels pretty good.
Sand down the ends that touch the joycons!
Just want to make sure you don't ruin your controllers by forcing them into the print
print it straight up so the adapters to the controllers don't get supports in them.
Make sure to sand down the connections to the joycons. They might be a little snug at first, so sand them down to not damage the controllers.